1. Field of the Invention
The present invention relates to ophthalmoscopy lens systems, particularly those employed with a slit lamp or other biomicroscope for the diagnosis and/or treatment of the eye.
2. Description of Related Art
During the diagnosis and treatment of the eye, it is typically necessary to provide a means for viewing various structures within the eye. Various ophthalmoscopy lens systems have been developed for this purpose. By way of example, “indirect” ophthalmoscopy lens systems have been developed. Such lens systems produce an aerial image of structures within the patient's eye, and such real images may be viewed using, for example, a slit lamp biomicroscope or other indirect ophthalmoscope. Direct ophthalmoscopy lens systems, on the other hand, produce a virtual image within the eye of structures within the patient's eye, such as the fundus (including the retina). The virtual image produced by direct ophthalmoscopy lens systems can be readily viewed by the practitioner. In general, direct ophthalmoscopic lens systems can provide greater magnification than indirect ophthalmoscopy lens systems, however, direct lens systems generally provide a smaller field of view.
The field of view provided by an ophthalmoscopy lens system can be significant in the diagnosis and treatment of certain eye conditions. In particular, special “gonioscopic” lens systems have been developed for viewing the anterior chamber angle of a patient's eye. The “anterior chamber angle” refers to the geometric angle where the iris and cornea meet. Fluid within the eye drains through the anterior chamber angle into channels which provide drainage. If the anterior chamber angle is narrowed, fluid flow may be obstructed resulting in an increase in pressure within the eye. Such an increase in pressure is often associated with glaucoma. Therefore, the diagnosis and treatment of glaucoma typically requires that the practitioner examine the anterior chamber angle. Observation of the anterior chamber angle, however, generally requires a lens systems which provides an extremely wide field of view.
Most gonioscopic lenses used to examine the anterior chamber angle rely on mirrors in order to achieve the required field of view (such as a “Goldmann” lens). Alternatively, U.S. Pat. No. 6,164,779, which is incorporated herein by way of reference, discloses various gonioscopic lens systems, many embodiments of which do not rely upon reflective surfaces for providing the desired field of view.